The invention relates to an apparatus for accurately dosing fluids of varying viscosity, especially highly viscous liquids, such as syrups having a high sugar content, comprising a substantially vertically arranged valve channel connectible to a storage container or the like, wherein for closing and opening a valve outlet there is provided a closure portion magnetically liftable against gravity, said valve channel being surrounded by an electromagnetic device for generating the magnetic force.
2. Description of the Prior Art
Measures by means of which the outflow quantity of a fluid can be timed are known. To this end provision is made that the static pressure determining the outflow quantity is maintained constant independently of the respective level of the liquid contained for instance in a storage container (see U.S. Pat. No. 3,258,166). This involves the disadvantage that said measures are effective only provided the fluid always retains the same viscosity and the same flowability independently of time and ambient temperature. However, if by temperature influences or the like the viscosity varies, though the delivery time and the pressure decisive for the outflow quantity remain constant, the amount of fluid discharged within the same time is subjected to changes. Hence, an accurate dosing is possible only on the condition that the device operating according to this principle is provided with a means for preventing changes both as regards temperature and viscosity.
For this reason, it has been known in connection with highly viscous liquids, for instance syrups having a high sugar content, to dose by volume. This permits dosing independently of the viscosity and the variations thereof at almost constant rates. But this system suffers from the disadvantage that no flowing adjustment is possible and that volumetric dosing is subjected to changes as a function of the ambient temperature in so far as the velocity of outflow of the fluid from the volumetric dosing chamber is never constant. To this must be added that, due to the great changes in viscosity, the marginal adhesion of the fluid in the volumetric measuring chamber varies to a large extent. This is likely to result in inaccuracies as to dosing. This applies especially to those cases in which the surface subjected to marginal adhesion is generally large as compared to that of the amount to be dosed. Besides, in such a case it is not possible, either, to completely eliminate the difficulties arising from varying viscosity due to great changes in ambient temperature.
It is the problem of the present invention to remove these difficulties and to provide a simple apparatus for accurately dosing fluids of varying viscosity, which is free from the mentioned disadvantages and particularly suited for accurately dosing small quantities, especially of highly viscous liquids. The device is particularly suited for dosing syrups having a high sugar content.